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ARS Home » Midwest Area » West Lafayette, Indiana » National Soil Erosion Research Laboratory » Research » Publications at this Location » Publication #306057

Title: Modeling conservation practices in APEX: From the field to the watershed

item Francesconi, Wendy
item Smith, Douglas
item Flanagan, Dennis
item Huang, Chi Hua
item WANG, XIUYING - Texas A&M University

Submitted to: Journal of Great Lakes Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2015
Publication Date: 5/14/2015
Publication URL:
Citation: Francesconi, W., Smith, D.R., Flanagan, D.C., Huang, C., Wang, X. 2015. Modeling conservation practices in APEX: From the field to the watershed. Journal of Great Lakes Research. 41(3):760-769.

Interpretive Summary: Taking advantage of the calibrated and validated APEX model for one of NSERL’s monitoring field sites, research was conducted modeling various conservation practices. A total of 13 single practices where simulated, and these were combined into pairs and groups of three to analyzed scenarios were multiple practices were adopted. The results indicate that the aggregate effect of combining several practices could more systematically reduce the loss of sediments and nutrients, and help improve the water quality problems associated with agriculture in the US Midwest.

Technical Abstract: The evaluation of USDA conservation programs is required as part of the Conservation Effects Assessment Project (CEAP). The Agricultural Policy/Environmental eXtender (APEX) model was applied to the St. Joseph River Watershed, one of CEAP’s benchmark watersheds. Using a previously calibrated and validated APEX project, the simulation of various conservation practices (single and combined) was conducted at the field scale. Seven variables (Runoff, Sediments, Total Phosphorus (TP), Dissolve Reactive Phosphorus (DRP), Soluble Nitrogen (SN), Tile Flow, and Soluble Nitrogen in Tile (SN-Tile)), were compared between the simulated practices. Field-scale outputs were extrapolated to the areas encompassed by the different conservation practices at the watershed scale. Results are presented as percentage reductions compared to the baseline scenario. When single conservation practices were implemented, 39% for sediment, 7% for TP, and 24% for SN-Tile were reduced. In contrast, losses in DRP and SN increased by 5% and 57%, respectively. When the conservation practices were combined, percentage reductions increased for all variables. The total reductions for combined two and three practices were 68% and 91% for sediments, 35% and 74% for TP, 1% and 48% for DRP, -43% and 28% for SN, and 50% and 85% for SN-Tile. Negative reductions were due to the slightly higher DRP and SN loads in no-till, mulch-till, and Conservation Crop Rotation practices, and their greater extent of incorporation at the watershed scale. Overall, the cumulative and combined effect of field conservation practices can help address the watershed’s excess nutrient and sediment concerns and improve water quality.